I'm trying to extract and stitch maf blocks from the UCSC Drosophila alignment that uses the most recent version of the D. melanogaster reference (BDGP R6). This build is not yet available as a built-in reference, so I was trying to add it as a custom reference. However, when running the Stitch Gene Blocks utility, I am told the bed file has an Unspecified genome build. Despite loading the BDGP R6 genome into galaxy as a fasta file, I am unable to choose a custom build for the bed file and am limited only to those genome builds that are pre-loaded. How can I get around this? Thanks.